Auxiliary starting switched reluctance motor

Abstract

A dynamo-electric machine such as a switched reluctance motor (10). A stator (14) has a central bore (16) and a plurality of inwardly salient poles (18A-18D) extending into the bore. A rotor (22) is mounted on a shaft (24) for rotation relative to the stator. The rotor has a plurality of outwardly salient poles (26A, 26B) extending into the bore. Stator windings (20, 21) are bifilar windings which produce an electromagnetic field when a phase is energized. The bifilar windings return energy to the voltage source when the phase is de-energized. An auxiliary winding (28) is also installed on the stator. The auxiliary winding is energized, when the machine is off, to produce a magnetic field which causes rotation of the rotor to a preferred aligned position relative to the stator poles. This facilitates subsequent starting of the machine. An electrical circuit (30) energizes the auxiliary winding, when the machine is off; and then energizes the stator windings when the machine is started. The circuit de-energizes the auxiliary winding when the stator windings are energized. The auxiliary windings are also effective when used with motors having a stepped air gap (G) between the stator poles and rotor poles, or when the stator has a shifted pole configuration.

What is claimed is: 
     
       1. A switched reluctance machine comprising: a stator assembly including a stator defining a plurality of stator poles;   a rotor mounted on a shaft and positioned for rotation relative to the stator, the rotor defining a plurality of rotor poles;   a stator winding installed on the stator assembly, the stator winding being adapted to be energized during normal operation of the machine to produce rotation of the rotor, the stator winding having a first given number of ampere-turns; and   an auxiliary starting winding installed on said stator assembly, the auxiliary starting winding being adapted to be energized to produce rotation of the rotor towards a position where the inductance of the auxiliary winding is maximized, the auxiliary starting winding having a second given number of ampere-turns, wherein the second given number of ampere-turns is greater than the first given number of ampere-turns such that, when energized with the same peak current, the torque produced on the rotor by energization of the auxiliary starting winding is greater than the torque produced by energization of the stator winding.   
     
     
       2. The switched reluctance machine of claim 1 wherein: the stator winding comprises a plurality of coils and each stator winding coil is positioned about a stator pole, each stator pole defining a base, each base defining a width; and   the auxiliary winding comprises a plurality of coils and each auxiliary winding coil is positioned about a stator pole;   and wherein the bases of the stator poles about which the auxiliary winding coils are positioned are reduced with respect to the bases of the stator poles about which the stator winding coils are positioned, such that the widths of each base of each stator pole about which an auxiliary winding coil is wound is less than the width of each base of each stator pole about which a stator winding coil is wound.   
     
     
       3. The reluctance machine of claim 1 wherein the stator defines inter-pole stator slots and wherein each stator slot includes conductors from the stator winding and conductors from the auxiliary winding. 
     
     
       4. The reluctance machine of claim 3 wherein the portion of each stator slot that is filled by conductors from the stator winding is greater than the portion of the stator slot filled by conductors from the auxiliary winding. 
     
     
       5. The reluctance machine of claim 1 wherein the rotor poles have stepped outer faces to form a stepped air-gap with respect to the stator poles. 
     
     
       6. The reluctance machine of claim 1 wherein there are N rotor poles, N being an integer, and wherein the stator winding is adapted to energize N stator poles and the auxiliary winding is adapted to energize N stator poles. 
     
     
       7. The reluctance machine of claim 1 wherein the stator winding is a bi-filar winding. 
     
     
       8. A switched reluctance system comprising: a reluctance machine including a rotor defining a plurality of rotor poles, a stator defining a plurality of stator poles, a single-phase winding positioned within the stator and adapted to be energized to establish rotation of the rotor, and an auxiliary winding positioned within the stator, the auxiliary winding being positioned such that energization of the auxiliary winding will energize at least one stator pole;   a first control circuit coupled to the single-phase winding to selectively energize the single-phase winding to establish rotation of the rotor in a desired direction with a given torque; and   a second control circuit coupled the auxiliary winding to energize the auxiliary winding in such a fashion that the rotor tends to rotate to a position where at least some of the rotor poles are in alignment with the stator pole energized by the auxiliary winding with a given peak torque that is greater than the peak magnitude of the torque imparted on the rotor when the single-phase winding is energized.   
     
     
       9. The reluctance machine system of claim 8 wherein the first control circuit is adapted to selectively energize the single-phase winding in response to a signal representative of the position of the rotor relative to the stator. 
     
     
       10. The reluctance machine system of claim 8 wherein the second control circuit is adapted to energize the auxiliary winding for a predetermined period of time during start-up of the machine to ensure reliable starting of the machine. 
     
     
       11. The reluctance machine system of claim 8 wherein the second control circuit comprises circuitry for detecting that the rotor is not rotating during a time when the single-phase winding is being energized and circuitry to energize the auxiliary winding for a predetermined duration when it is determined that the single-phase winding is being selectively energized and the rotor is not rotating. 
     
     
       12. The reluctance machine system of claim 8 wherein the second control circuit comprises circuitry for detecting the angular position of the rotor and circuitry to energize the auxiliary winding until the rotor reaches a preferred aligned position. 
     
     
       13. The reluctance machine system of claim 8 wherein the first control circuit is coupled to a DC bus and includes a switchable element to provide power from the DC bus to the single phase winding and wherein the second control circuit is coupled to a source of AC power and wherein the second control circuit includes a switchable element to energize the auxiliary winding with AC power. 
     
     
       14. The reluctance machine system of claim 8 wherein the second control circuit comprises a relay. 
     
     
       15. A method of operating a single-phase reluctance machine, the machine comprising a rotor, a stator, a single-phase main winding positioned within the stator, and an auxiliary winding positioned within the stator, the method comprising the acts of: receiving AC power from an AC power source;   converting the AC power to DC power and providing a DC power bus;   energizing the auxiliary winding with the AC power to cause rotation of the rotor towards a desired rotor position; and   selectively energizing the single-phase main winding with power from the DC bus to establish rotation of the rotor relative to the stator.   
     
     
       16. The method of claim 15 wherein the act of energizing the auxiliary winding is performed upon start-up to position the rotor at a preferred starting position. 
     
     
       17. The method of claim 15 wherein the act of energizing the auxiliary winding is performed when it is determined that the rotor is not rotating during normal operation to impart a unjamming torque to the rotor. 
     
     
       18. The method of claim 15 wherein the act of energizing the auxiliary winding is performed to brake the motor. 
     
     
       19. A switched reluctance machine system comprising: (i) a power controller; and   (ii) a switched reluctance machine coupled to the power controllers the switched reluctance machine comprising:   a stator assembly including a stator having a central bore and a plurality of inwardly salient poles extending into said bore;   a rotor mounted on a shaft and installed in said central bore for rotation of said rotor relative to the stator, said rotor having a plurality of outwardly salient poles extending into said bore, there being an air gap between the respective outer ends of said stator and rotor poles;   stator windings installed on the stator assembly, said stator windings being energized by the power controller when said machine is running to produce a magnetic field producing a rotation of the rotor at a given peak torque; and   an auxiliary winding installed on said stator assembly, said auxiliary winding being adapted to be energized by the power controller when the machine is not running to produce rotation of the towards a position where the inductance of the auxiliary winding is maximized to facilitate starting of the machine, the peak torque produced by energization of the auxiliary winding being greater than the peak torque produced by energization of the stator winding.   
     
     
       20. An improved blender comprising: a chopping member;   a reluctance machine having a stator, a rotor mounted to a shaft and positioned to rotate relative to the stator, a single-phase winding positioned within the stator, and an auxiliary winding positioned within the stator, the chopping member being coupled to the rotor shaft;   a first control circuit for selectively energizing the single-phase winding to produce rotation of the rotor with a given average running torque; and   a second control circuit for selectively energizing the auxiliary winding to produce a peak torque that tends to move the rotor to a desired position relative to the stator that is greater than the average running torque produced when the single-phase winding is energized.